Malmgrenia castanea McIntosh 1876

Malmgreniella castanea (McIntosh, 1876)

Eunoa n. sp.—McIntosh, 1868:337, 338.

Malmgrenia castanea McIntosh, 1876a:376, pl. 67: figs. 15–19; pl. 68: fig. 15; 1900:379, pl. 28: fig. 15; pl. 30: fig. 5; pl. 33: fig. 10; pl. 40: figs. 23–26.—Allen, 1915:612.—Fauvel, 1923:48, fig. 17h–m.—Ditlevsen, 1929:5.—Støp–Bowitz, 1948:7, fig. 3.—Plymouth Marine Fauna, 1957:110.—Picard, 1965:53 [footnote].—Intes and Le Loeuff, 1975:273.—Kudenov, 1975b:79.

Laenilla castanea.—Giard, 1886:3, figs.

Polynoe (Malmgrenia) castanea.—Hornell, 1891:235.

Harmothoe castanea.—Saint-Joseph, 1898:236.—Ditlevsen, 1917:27, figs. 9, 10.—Tebble and Chambers, 1982:47, figs. 15, 44, 45.—Hanley, 1987:151, fig. 3E.

Malmgrenia lunulata.—Pettibone, 1953:25 [part; not Delle Chiaje, 1830].

Harmothoe lunulata.—Pérès, 1954:92.—Bellan, 1964:27 [part].—Picard, 1965:53 [part]. [Not Delle Chiaje, 1830.]

MATERIAL EXAMINED.—NORTHEASTERN ATLANTIC OCEAN: Norwegian Sea: 50°57′N, 10°46′W, 184 and 200 m, Michael Sars sta 96, 27 Jul 1910, 2 specimens (ZMUB 29582, 41504, identified by Støp-Bowitz, 1948). Shetland Islands: 25 mi NNE of North Unst, 155 m, shell and sand, 1868, on Spatangus purpureus O.F. Müller, G. Jeffreys, collector, 6 syntypes of Malmgrenia castanea (BMNH 1921.5.1.507; ZMB 1162; USNM 54714). SW Ireland: 50 mi west of Valentia, 146–201 m, G. Jeffreys, collector, 2 syntypes of Malmgrenia castanea (BMNH 1921.5.1.509). Channel Islands: Off St. Peter Port, Guernsey, 9–13 m, 1868, syntype of Malmgrenia castanea (BMNH 1921.5.1.508). English Channel: 50°21′N, 03°01′W, 53 m, Manihine sta 69, 30 Aug 1949, 1 specimen (BMNH 1950.6.6.1). England: Plymouth area, Eddystone, on Spatangus purpureus, shell and gravel, 26 Mar 1953, 24 Mar 1960, G.M. Spooner, collector, 2 specimens (LCHP–S-21). Plymouth area, P. Gibbs, collector, 2 specimens (LCHP–G-3; USNM 55047).

MEDITERRANEAN SEA: France: Marseille, 8 m, on oral surface of Spatangus purpureus, in Amphioxus sand, G. Bellan, collector, 1 specimen (USNM 59929).

DESCRIPTION.—Nine syntypes mostly fragmented. Length of complete syntype 15.5 mm, width including setae 6 mm, with 38 segments. Length of 2 specimens from Norwegian Sea 20–21 mm, width 7–8 mm, with 38 segments. Length of 4 specimens from Plymouth area 8–15 mm, width 2.5–8 mm, with 34–39 segments. Body elongated, flattened, tapering slightly anteriorly and posteriorly. Dorsum, exposed part of elytra, and dorsal cirri with light to dark brownish pigmentation. Elytra 15 pairs, on usual segments, large, covering dorsum, round to subreniform, without papillae, with group of microtubercles on anterior part but absent on first pair and some posterior elytra (Figure 20B–E; McIntosh, 1900, pl. 33: fig. 10).

Bilobed prostomium truncate anteriorly, without distinct peaks; eyes moderate in size, anterior pair slightly anterior to greatest width, slightly larger than posterodorsal pair; ceratophore of median antenna in anterior notch, with style longer than prostomium; ceratophores of lateral antennae inserted terminoventrally, with styles short, subulate; palps stout, tapered; tentaculophores without setae, dorsal and ventral tentacular cirri similar to median antenna (Figure 20A; McIntosh, 1900, pl. 28: fig. 15; Støp-Bowitz, 1948, fig. 3). Segment 2 with first pair of large elytrophores, biramous parapodia, and long ventral buccal cirri similar to tentacular cirri; notosetae similar to following notosetae; neurosetae more slender than those following, with entire bulbous tips (Figure 20A,F,G). Extended pharynx with 9 pairs of border papillae and 2 pairs of jaws.

Biramous parapodia with translucent, pale setae; notopodium shorter than neuropodium, subconical, with projecting acicular lobe on lower side; neuropodium with subconical presetal acicular lobe with thick supraacicular process and shorter rounded postsetal lobe (Figure 20H,I; McIntosh, 1900, pl. 30: fig. 5). Notosetae moderate in number, short to long, slightly stouter than neurosetae, slightly curved, tapering toward tips, with faint spinose rows (Figure 20J; McIntosh, 1876a, pl. 67: fig. 15; 1900, pl. 40: fig. 23). Neurosetae moderate in number, with faint spinose regions, slightly hooked tips, some with very small secondary tooth (Figure 20K; McIntosh, 1876a, pl. 67: figs. 16–19, 1900; pl. 40: figs. 24–26). Cirrophores of dorsal cirri cylindrical, wider basally, with styles smooth, tapered distally, extending to tips of neurosetae or beyond; dorsal tubercles bulbous; ventral cirri short, subulate (Figure 20H; McIntosh, 1900, pl. 30: fig. 5). Pygidium medial to last pair of small parapodia, with pair of long tapered anal cirri.

BIOLOGY.—Malmgreniella castanea is commensal with spatangid echinoids. It has been found clinging to the test near the mouth of the burrowing spatangid Spatangus purpureus O.F. Müller.

DISTRIBUTION.—Northeast Atlantic Ocean, Norwegian Sea, Shetland Islands to Mediterranean Sea. In 8–878 meters (see McIntosh, 1876a).